Angioplasty is an excellent method for treating a wide variety of vascular diseases. In particular, it has been used extensively for opening stenoses in coronary arteries. The process has been increasingly used for treatment of stenosis in other parts of the vascular system.
One of the more well known and widely practiced forms of angioplasty makes use of a dilatation catheter which has an inflatable balloon at is distal end. Using fluoroscopy, the physician guides the catheter through the vascular system until the balloon is properly positioned. By applying a fluid through the separate inflation lumen, the balloon is inflated. The balloon's inflation causes the artery to stretch and presses the lesion or stenose into the artery wall, thereby reestablishing after deflation of the balloon, increased blood flow through the artery.
In order to treat very tight stenoses, i.e., those having small openings, increasingly small catheter diameters are desirable. significantly more flexible catheters are also desired in that otherwise very tight areas of stenosis will not be approachable. Although flexible and narrow of diameter, a good catheter must also be easily introduced and easily advanced through the tortuous path of the vascular system.
There are a variety of dilatation catheter types. Many use multiple lumens. For instance, a catheter may use a separate guidewire lumen so that a guidewire can be used to establish the path to the stenosis. The catheter may then be fed over the guidewire until the balloon is positioned over the stenosis. The catheter obviously has a separate lumen to allow introduction of and removal of fluid for the balloon.
Other catheter designs include those which act as their own guidewire, thereby eliminating the need for a separate guidewire lumen. Elimination of the need for the separate lumen means that the profile of the catheter can be somewhat smaller. Typical of such integral designs are U.S. Pat. No. 4,606,247, to Fogarty et al., which shows a catheter having an evertible balloon at is distal tip. The distal tip of the catheter is placed near the stenosis to be treated. The balloon is extended beyond the distal tip to a position within the stenosis and then inflated to press the lesion back into the wall of the vessel. The balloon contains a passageway in the middle having a plug of some elastomeric material through which a guidewire may be placed. The plug retains the pressure of the fluid on the balloon, whether the guidewire is present or not.
Another "over-the-wire" catheter is shown in U.S. Pat. No. 5,085,636, to Burns. The Burns device utilizes a balloon having a port for introducing fluid into the balloon and simultaneous device for not allowing fluid to pass through the catheter when a guidewire is present in the vicinity of the balloon. The fluid seal is distendible and does not allow fluid past the guidewire.
My U.S. Pat. No. 5,171,221, entitled "Single Lumen Low Profile Valved Balloon Catheter" discloses a single lumen balloon catheter having a catheter using a flexible guidewire which extends axially through the lumen beyond the open end of an intermediate balloon segment. The guidewire is axially movable within the lumen and has two discrete portions of different diameters. The first diameter, distal on the guidewire, is smaller that a second more proximal diameter on the guidewire. The larger guidewire meshes with the diameter of the lumen just proximal of the balloon thereby sealing it on the proximal end. Simultaneously at the distal end of the balloon a valve member mounted on the guidewire blocks the distal opening of the catheter.
None of the prior art shows a device in which a control wire having a valve plug mounted thereon, which meshes with a valve seat mounted within the lumen and in which the balloon maintains a constant axial length during its distension.